1. Field of Invention
The present invention relates to concentration determination of organic additives contained in a metal electroplating solution, and more specifically to a method for determining concentration of suppressor, accelerator, and/or leveler in aqueous acid metal electroplating solutions, by mathematically eliminating the cross-interference between the effects of these additives.
2. Related Art
The Pulsed Cyclic Galvanostatic Analysis (PCGA) provides a method for accurately determining the variety of organic constituents usually contained in metal electrochemical plating baths, such as suppressors, accelerators, and levelers. It is a chrono-potentiometric method wherein the plating currents are set constant, and plating over-potentials are conveniently measured and used to quantify the concentrations of various constituents in the electrochemical plating baths.
Robertson U.S. Pat. No. 6,280,602 (hereinafter “Robertson patent”) discloses a PCGA-based method and apparatus for indirect determination of the concentrations of various organic additives in the metal plating baths, which is capable of determining such concentrations with a high degree of accuracy (usually less than 10 percent of error rate).
However, the Robertson patent does not take into account the interacting and interfering effects of various additives on the measured electroplating potential, which may affect the accuracy of the calculated additive concentrations based on such measured electroplating potential. For example, the increment of the leveler concentration in the metal plating bath reduces the accelerator response, leading to under-reading of the accelerator concentration, while the increment of the accelerator concentration increases the leveler response, leading to over-reading of the leveler concentration.
Therefore, it is an object of the present invention to provide a method for correcting the additive concentrations calculated, according to the conventional PCGA-based method, so as to eliminate the interaction and interference between various additives.
Other objects and advantages will be more fully apparent form the ensuing disclosure and appended claims.